Heating device for machines for the transformation of plastic materials

ABSTRACT

The heating device for a machine for transforming plastic materials, comprises a heating body (39) disposed between two parallel rows (41, 42) of preforms (14). It is provided with at least two heating tubes (40) having bidirectional heating blades (54). These latter are inclined at an angle (α) such that a first of their faces emits heating radiation (55) in the direction of the adjacent row of preforms and such that the second surface emits its heating radiation (56) substantially in the direction of the free space between the two opposite rows of heating tubes toward the farthest row of preforms. Reflectors (60) are moreover arranged so as to reflect the heating radiation in a horizontal plane toward the preforms (14). The device thus permits obtaining very high energy efficiency whilst avoiding a harmful elevation of the temperature of the machine into which it is integrated.

The present invention relates to a heating device for a machine for thetransformation of plastic material, comprising, arranged along a guidetrack, a heating device adapted to coact with at least one row ofpreforms carried by supports moved through the heating device, thislatter having a heating body arranged facing the preforms.

There is known from Swiss patent 683.757, a machine for thetransformation of plastic materials, in the form of a machine for theproduction of receptacles from PET, comprising a heating device. In thisdevice, the preforms aligned in a single row are displaced in theheating device which comprises infrared lamps disposed on two sidesalong the row of preforms.

To heat a single row of preforms, the heating device therefore has twoheating bodies with infrared lamps. A large portion of the energy ofthese latter is not specifically directed toward the preforms to beheated, but dispersed laterally and upwardly and downwardly into thegeneral area of the heating device and of the machine. The known heatingdevice is thus less economical and produces a rise in the environmentaltemperature which is undesirable, or even harmful.

The present invention has for its object to overcome these drawbacks andit is characterized to this end by the fact that the heating bodycomprises at least two heating tubes each containing a bidirectionalheating blade adapted to emit heating radiation to two opposite sides,the two tubes being adapted to be arranged between the two parallel rowsof preforms to form a heating body of which each of the heating bladesis inclined at a predetermined angle relative to a vertical plane suchthat a first of its surfaces emits heating radiation in the direction ofthe adjacent row of preforms and such that the second surface emitsheating radiation toward the farther row of preforms substantially inthe direction of the space which is not covered by the opposite heatingtube or tubes.

There is thus obtained a heating device with a very high energyefficiency. The radiation emitted by the heating tubes is directedprecisely toward the preforms to be heated and a single heating bodysuffices to heat simultaneously two rows of preforms. Regions shadedfrom the heating radiation of the preforms are avoided. The heatingpower can thus be greatly decreased, from which result substantialsavings of energy. The general environment of the machine may thusremain at a lower temperature.

Preferably, the device comprises at least four heating tubes to comprisea heating body of polygonal cross section, each of the heating bladesbeing inclined at a predetermined angle α relative to a vertical planesuch that said second surface emits heating radiation in the directionof the free space between the opposed heating tubes toward the fartherpreforms.

The geometric arrangement of the heating radiation in thus particularlywell distributed and balanced without giving rise to shaded zones and byavoiding in an optimal manner energy losses.

According to a preferred embodiment, the heating body has asubstantially rectangular cross section and a horizontal and verticalposition of the heating tubes relative to the frame of the heating bodyand said predetermined angle are adjustable as a function of the size ofthe preforms.

These characteristics ensure very effective heating at a high output. Itis also possible to heat differentially certain regions as a function ofthe ultimate transformation desired.

Very favorably, the heating device comprises reflectors arranged in anexternal position relative to the heating tubes and to the preforms andshaped so as to reflect the heating radiation emitted by the heatingtubes disposed nearest the reflectors in the direction of the preformsof the farthest row of preforms through the free space between twosuccessive preforms of the nearest row.

There is thus obtained also an optimum horizontal thermal distributionconcentrating all of the radiation toward the preforms to be heated. Theefficiency is thus again significantly improved, giving rise tosubstantial savings of energy.

Preferably, the reflectors are of cylindrical incurved shape and of awidth substantially equal to the distance separating the centers of twosuccessive preforms.

This arrangement permits a simple construction ensuring high energyefficiency.

According to a preferred embodiment, the heating device comprises aventilating device comprising means adapted to direct separate airflowstoward the heating tubes, through the two rows of preforms and towardtheir supports.

These characteristics ensure separate effective ventilation and cooling.

The ventilation device thus comprises preferably a horizontal walladapted to separate a lower aeration channel in which are located thesupports of three upper aeration channels comprising a central channeladapted to direct air toward the heating tubes and two lateral channelsadapted to direct air toward the preforms.

Each portion of the heating device can thus be cooled or subjected to achange of air in a differentiated manner.

Preferably, said reflectors constitute simultaneously deflectors adaptedto direct air from the lateral channels toward the preforms.

There is thus obtained a particularly simple construction, whilstavoiding effectively undesired heating of the reflectors.

Other advantages will appear from the characteristics set forth in thedependent claims and in the description given hereafter of the inventionin greater detail with the aid of drawings which show schematically andby way of example one embodiment.

FIG. 1 is a schematic plan view of a machine for the transformation ofplastic material in which the heating device according to the inventionis integrated.

FIG. 2 is a plan view of the heating device.

FIG. 3 is a view in.longitudinal cross section through the heatingdevice.

FIG. 4 is a view in transverse cross section through the heating device.

FIG. 5 is a fragmentary horizontal sectional view through the heatingdevice.

Referring to FIG. 1, the machine for the transformation of plasticmaterial, such as a machine for the production of receptacles of plasticmaterial by draw-blowing in which the heating device 10 according to theinvention is integrated, comprises a frame 12 on which the variousdevices and members of the machine are mounted in modular fashion.Preforms 14 for the receptacles to be produced are supplied by means ofa double rail 15 forming an inclined plane to reach an inverting loadingdevice known per se, shown schematically at 16, in which the preformsare inverted and disposed neck down in supports 17 carried by carriers18, each carrier carrying two supports 17.

The preforms 14 are then heated in the heating device 10 and moved to ablowing or draw-blowing device 19. After their formation, thereceptacles are removed from the supports 17 into an inverting dischargedevice 20, from which they can be treated according to their future useor moved toward sterilization, filling, labelling, packaging stations,etc.

The empty supports 17 carried by the carriers 18 are then moved to theloading device 16 for the preforms.

The carriers 18 are constituted by plates 22 (FIG. 4) of elongatedrectangular shape with rounded ends, comprising two bores 23 in whichthe supports 17 are maintained. These plates 22 rest laterally on aguide track 24 comprising two lateral rails 25, 26 that touch eachother. This guide track comprises two separate portions 28, 29.

A first portion 28 comprises the outlet of the heating device 10, thedrawing-blowing device 19, the discharge device 20 and the connectionpath to the discharge device 16 and the loading device 16 of thepreforms 14. In this first portion 28, the plates 22 touch with theirrounded ends and are aligned one behind the other thereby forming asingle row of supports 17 and preforms 14.

On the other hand, in the second portion 29 of the guide track 20, theplates 18 touch in particular by their long sides and thus form twoparallel rows of preforms 14, the two supports 17 of each carrier 18being aligned in a direction perpendicular to the direction of movementof the carriers.

Of course the number of parallel rows of carriers 18 in the secondportion 29 could be greater than one according to the uses and the sizeof the machine. This second portion 28 will nevertheless comprise atleast one row of carriers 18, and hence two parallel rows of preforms 14and of supports 17 aligned in the direction of movement in the path ofthe guide track in the heating device 10, as well as at its inlet and atits outlet.

The movement of the carriers 18 in the first and second portions 28, 29of the guide track is obtained by pushing by means of jacksschematically indicated at 32 and 33. Given that this guide track 24constitutes a closed circuit, the linear speed of displacement isgreater in the first portion 28 than in the second portion 29. Thispermits gradual and optimum heating of the preforms for a predeterminedtime. As the heating phase of the preforms requires a greater time thanthe other phases and operations of production, there is obtained acontinuous operation with very high output, whilst reducing the lengthof the production track and hence the overall size of the machine.

The construction of this heating device 10 is explained in greaterdetail with reference to FIGS. 2 to 5 and comprises an oven 25 with amovable frame 36 mounted vertically slidably on the frame 12. Thanks topneumatic jacks 37, this oven 35 can be raised from an active position(FIGS. 3 and 4) to an inactive position during interruption in theproduction or during stopping or starting of the machine. Thus, thelarge number of preforms located in the oven is not damaged. Thus, evenwhen the oven is turned off during an interruption, the remaining heatafter stopping the oven runs the risk of severely damaging the preformslocated in the oven. With a movable oven, this drawback is entirelyovercome.

The oven 35 comprises a heating body 39 suspended from a movable frame36. This heating body comprises at least two bidirectional heating bladetubes 40 of carbon extending longitudinally over the greater portion ofthe oven. The number of pairs of heating blade tubes depends inparticular on the length of the preforms to be heated, in theillustrated example two pairs of tubes are shown. These tubes 40 arearranged so as to emit heating radiation directed to two opposite sides.

The heating body 39 is in active position disposed between two rows 41,42 of preforms so as to heat simultaneously the preforms 2 of these tworows between which it is disposed. This heating body 39 and the two rowsof preforms associated therewith are surrounded by a heating hood 46fixed to the frame 36. On the hood, the supports 17 for the preforms areprotected by a protective profile 48. A fan 71 (FIGS. 2 and 3) disposedat the outlet of the oven 40 ensures change of air in the heating zone.

Referring to FIG. 4, the preforms 14 are disposed, neck down, in theupper portion of the support 17 constituted by an annular retentionmember 50. These supports 17 comprise a tubular portion passing throughbearings engaged in bores 23 of the plates 18. These bearings 52 arealso retained by means of an annular groove on the rails of the guidetrack 24 on which the plates 18 rest.

The supports 17, at their lower end, are secured to a drive pinion 51.

The second portion 29 of the guide track 24 is provided with a drivemechanism for rotation of the preforms 14. This mechanism (not shown)comprises a chain or belt arranged parallel to the guide track betweentwo pinions and driven by a motor, to coact with the pinions 51 so as torotate the supports 17 and the preforms 14 during their passage throughthe heating device 10.

Referring to FIG. 4, the four tubes 40 with bidirectional heating blades54 of the heating body 39 are arranged in a generally rectangulararrangement with horizontal spacing A and vertical spacing B that isadjustable. Each heating blade 54 has an adjustable angle α with avertical plane, such that its forward face emits its heating radiationsubstantially at an angle of incidence of 90°-α toward the adjacentpreforms 41, 42 and such that its rear face emits its heating radiationbetween the opposite tubes toward the preforms of the farther row. Thecenters of the forward and rear beams of radiant heat emitted by eachtube 40 are schematically indicated by arrows 55, 56 in FIG. 4.

The combined forward and rearward heating radiation of the four tubes 40thus permits obtaining a highly effective heating directed over all theheight of the preforms 14, but delimited to this height. Upwardly anddownwardly, the heating radiation diminishes very sharply in the centralportion as is indicated by the curves 58, 59 of hyperbolic appearancecorresponding to the isothermal curves. The energy losses due toradiation directly upwardly and downwardly are therefore greatlyreduced. Given that the major portion of the heating radiation emittedby the rear surface of the heating blades 54 is directed between theopposite heating tubes, regions shaded from heating radiation on thepreforms 14 are avoided.

By adjustment in horizontal and vertical translation of each of theheating tubes 40 relative to the frame of the heating body 39 and byadjustment to a suitable angle α of inclination, it is possible tooptimize the exact geometric distribution of the heating radiation in aplane perpendicular to the heating body 39 and this for all shapes andsizes of preforms 14. Considerable savings of energy can thus berealized by this favorable arrangement of the elements of the heatingbody.

It is also possible to heat differentially certain regions of thepreforms more or less strongly as a function of the ultimate desiredtransformation of the plastic material.

Referring to FIGS. 2 and 5, the heating device 10 also comprises meansadapted to direct suitably the heating radiation so as to obtain anoptimum horizontal thermal distribution. These means are constituted byreflectors 60 fixed to the movable frame 36 outside the preforms 14.These reflectors 60 are of cylindrical shape with an incurved sectionand are shaped so as to reflect radiation 62 emitted between twoadjacent preforms of a row 41, such that the reflected radiation 63 willbe concentrated on a preform 14 located on the opposite row 42. Thereflectors 60 are disposed in a row one following another with acenter-to-center distance corresponding to that of two successivepreforms 14 of a row. Their width is substantially equal to the distanceseparating the centers of two successive preforms 14 (FIG. 2).

Thus, in the horizontal plane also, practically no, heating radiation islost by emission not directed against the preforms, which furtherpermits realizing energy savings.

The assembly of the vertical and horizontal means adapted to directheating radiation, produces the result that the energy emitted by theheating body is directed in an optimum and adjustable way against thepreforms. Heat losses are thus avoided as efficiently as possible. Theheating body 39 will therefore operate with greatly reduced power, whichpermits decreasing substantially the ambient temperature of the machine12 in which the heating device 10 is integrated.

Of course the heating body 39 could be present in a number greater thanfour heating tubes 40. Thus, for preforms of very great height, two oreven four or more tubes with inclined heating blades 54 could besuperposed to form two parallel rows separated by the distance A.

For short preforms, the heating body 39 could also have only two tubeswith inclined heating blade such that the second surface emits heatingradiation toward the farther row of preforms substantially in thedirection of the space not covered by the opposite tube.

Referring to FIGS. 2 and 3, the heating device 10 is provided with aventilation device 70 comprising a fan 71 disposed at the outlet of theoven 35 and adapted to blow air into the different portions of oven 35in a direction 72 opposite the direction of advance 73 of the preforms.

This ventilation device comprises four ventilation channels separatedin-the horizontal and the vertical plane. The protective profile 48separates the upper channels 75, 76, 77 from a lower channel 78, inwhich the supports 17 and the carriers 18 are cooled. Above the profile48, there is obtained through an upper central channel a replacement ofthe air surrounding the heating tubes 40, whilst two lateral upperchannels 66, 67, separated from the central upper channel 75 byreflectors 60, permit directing the air toward the preforms 14. Becauseof their incurved shape, the reflectors 60 are simultaneously deflectorsadapted to direct the ventilation air in the direction of the preforms14 and of the supports 17. There is thus obtained an efficient aerationabout the preforms 14 whilst cooling the reflectors 60. The ventilationair is evacuated from the oven by an outlet conduit 79.

Of course the embodiment described above is non-limiting and can be thesubject of any desirable modification to the interior of the frame asdefined by claim 1. Thus, the heating device 10 could be designed for alarger number of pairs of parallel rows of preforms and thus comprisesseveral heating bodies 19 arranged parallel to each other.

The machine 12 for transformation of plastic material could be of anyother nature. In particular, the movement of the carriers 18 could beeffected by any other actuating means such as pulleys and drive chains,indexed wheels coacting with supports 17 or with carriers 18. The guidetrack 20 could in particular in its first portion 28, have any othershape, for example a half circle or irregular.

The machine could be connected directly or indirectly to other devicesensuring ultimate treatment of the receptacles. It could also bepreceded by an installation for production of these preforms.

The ventilation device could be made in a different way, for examplewith an air flowing following a different path and comprising adifferent number of channels.

It could also comprise more than one fan or adjustable valves.

The reflectors 60 could have any other shape, for example inclined flatsurfaces.

The machine and its heating device are particularly well adapted for theproduction of receptacles of polyethylene terephthalate, but could alsobe adapted to use with other plastic materials.

I claim:
 1. Machine (12) fore transforming plastic material, comprising,arranged along a guide track (24), a heating device (10) adapted tocoact with at least one row of preforms (14) carried by supports (17)moved through the heating device (10), this latter having a heating body(39) arranged facing the preforms (14), characterized by the fact thatthe heating body (39) comprises at least two heating tubes (40) eachcontaining a bidirectional heating blade (54) adapted to emit heatingradiation to two opposite sides, the preforms being disposed in at leasttwo parallel rows of preforms in the heating device (10), the two tubesbeing adapted to be arranged between the two parallel rows of preformsto form a heating body of which each of the heating blades (54) isinclined at a predetermined angle (α) relative to a vertical plane suchthat a first of these surfaces emits heating radiation (55) in thedirection of the adjacent row of preforms and such that the secondsurface emits heating radiation (56) toward the farther row of preformssubstantially in the direction of the free space between the oppositeheating tube or tubes.
 2. Heating device according to claim 1,characterized by the fact that it comprises at least four heating tubes(40) to comprise a heating body (39) of polygonal shape, each of theheating blades (54) being inclined at a predetermined angle (α) relativeto a vertical plane such that said second surface emits heatingradiation (56) in the direction of the free space between the opposedheating tubes (40) toward the farther preforms.
 3. Device according toclaim 2, characterized by the fact that the heating body (39) has asubstantially rectangular cross section and by the fact that thehorizontal and vertical positions of the heating tubes (40) relative tothe frame (36) of the heating body and said predetermined angle (α) areadjustable as a function of the size of the preforms (14).
 4. Deviceaccording to claim 1, characterized by the fact that it comprisesreflectors (60) arranged in an external position relative to the heatingtubes (40) and to the preforms (14) and so shaped as to reflect theheating radiation emitted by the heating tubes (40) disposed nearest thereflectors (60) in the direction of the preforms (14) of the farthestrow of preforms through the free space between two successive preformsof the nearest row.
 5. Device according to claim 4, characterized by thefact that the reflectors (60) are of incurved cylindrical shape and of awidth substantially equal to the distance separating the centers of twosuccessive preforms.
 6. Device according to claim 1, characterized bythe fact that it comprises a ventilation device (70) comprising meansadapted to direct separate airflows through the heating tubes (40),toward the two rows (41, 42) of preforms (14) and toward their supports(17).
 7. Device according to claim 6, characterized by the fact that theventilation device (70) comprises a horizontal wall (48) adapted toseparate a lower air channel (78) in which is located the supports (17)of three upper aeration channels (75, 76, 77), comprising a centralchannel (75) adapted to direct air toward the heating tubes (40) and twolateral channels (76, 77) adapted to direct air toward the preforms(14).
 8. Device according to claim 4, characterized by the fact thatsaid reflectors (60) constitute simultaneously deflectors adapted todirect air from the lateral channels (76, 77), toward the preforms (14).9. Device according to claim 6, characterized by the fact that saidairflows (75, 76, 77) are directed in a direction (72) opposite that(73) of the advance of the preforms (14).
 10. Device according to claim1, characterized by the fact that it comprises carriers (18) eachsupporting two supports (17) and two preforms (14) arranged side by sideperpendicular to the direction of advance of the preforms at the heatingdevice (10), each carrier (18) being in contact with the preceding andfollowing one so as to constitute two parallel rows (41, 42) of preforms(14) between which the heating body (39) is adapted to be positioned.11. Device according to claim 1, characterized by the fact that theheating body (39) is movably mounted relative to said guide track (24)so as to be able to be displaced from an active position in which it isdisposed substantially facing the preforms (14) to an inactive positionin which it is spaced from the preforms.
 12. Device according to claim10, characterized by the fact that the heating body (39) is mounted on amovable frame (36), this latter being adapted to be displaced verticallyunder the action of a lifting device (37).